Boilers



Nov. 24, 1959 sMiTH BOILERS Filed June 13;-1955 3 Sheets-Sheet 1 Wen/me Nov. 24, 1959 w. H. SMITH 2,914,039

BOILERS Filed June 15. 1955 3 Sheets-Sheet 2 W. H. SMITH Nov. 24, 1959 BOILERS Filed June 13. 1955 3 Sheets-Sheet 3 Wyn/70 4/,

LLl/IM M5441 United States Patent 2,914,039 BOILERS William Herbert Smith, East Molesey, England Application June 13, 1955, Serial No. 515,203

6 Claims. (Cl. 122---379) This invention relates to boilers of the kind in which the combustion gases pass through a series of vertical tubes on their way to the flue from the combustion space. Water in spaces surrounding the tube is heated by heat exchange through the tube walls.

In order to improve efliciency, it has been proposed to place spiral elements in the tubes to cause the gases to travel a greater distance than the straight path through the tube and to cause them to impinge on the sides of the tubes before they pass out of the tubes to the flue passages.

With such an arrangement difliculty has been experienced in cleaning the tubes as is necessary at frequent intervals to ensure free passage of the gases.

In accordance with the invention, the spirals are lifted and lowered in the tubes when it is desired to clean the tubes, this movement cleaning the sides of the tubes and knocking off any deposit such as fly ash which has accumulated on the spiral elements.

From another aspect, the invention provides a boiler having a series of tubes through which the flue gases pass, spiral elements within the tubes and movable relatively to the tubes along the axis thereof and means to raise and lower the spiral elements whereby the tubes and elements are cleaned of deposits.

Preferably the elements are raised and/ or lowered with a sharp movement, for example by cams or the like. They may be raised together or sequentially in groups or individually.

The raising and lowering mechanism may be power operated, preferably in accordance with the output of the boiler. The output of the boiler is proportional to the number of revolutions of a fan which is operated periodically under the control of a thermostat and which supplies combustion air to the fuel. Means may be provided so that after a predetermined number of revolutions of the fan (or after the fan' has been running in total for a predeterminedtime) a motor driving the lifting mechanism for the tubes is operated and runs for a predetermined time during which the tubes are lifted and dropped a definite number of times.

The main flue passages may also be cleared of accumulated deposits by having a valve opening into the combustion chamber which leads to the ash pit and which is similarly controlled.

Other parts of'the invention are embodied in the preferred forms which will now be described in some detail by way of example with reference to the accompanying drawings in which: s

Figure 1 is a section through so much of a boiler having tubular flues as is necessary to illustrate the invention,

Figure 2 is a plan view of the form of Figure 1 having certain accessory parts shown diagrammatically,

Figure 3 is a view similar to Figure 1 of another form, and

Figure 4 is a plan view of the form of Figure 3.

Referring to the drawings, the flue gases pass from the combustion space to the flues through vertical tubes 1 arranged in a plurality of rows, these tubes being surrounded by water which is heated by heat exchange through the tube walls. Within each tube 1 is mounted a spiral element 2 having a projecting lug 3 by which the element rests on the top edge of the tube. The shaft 4 of the element is extended and formed with a mushroom head 5.

Adjacent each transverse row of tubes, there is mounted a cross-shaft 6 supported at each end in cradle bearings so that they can be readily lifted out whenever desired. Projecting from the shaft 6 are arms 7 which extend between the mushroom heads of two adjacent elements 2 and have at their ends a transverse arm 8 which engage below the mushroom heads. Also mounted on the shaft 6 is a lever 9 which projects upwardly.

Mounted above the cross-shafts 6 and transverse thereto is a thrust member 10 comprising a plurality of thrust pins 11 against which the levers 9 engage. The thrust member 10 is reciprocable longitudinally. When it is moved in one direction, the pins 11 move the levers 9 thereby rotating the cross-shafts causing the arms 7 to raise the spiral elements 2 in the tubes 1. When the thrust member is moved in the opposite direction, the Weight of the spiral elements causes them to drop sharply. The elements are thus jolted every time the thrust member 10 is reciprocated.

The arms 8 are arranged to contact the mushroom heads off-centre so that as the spiral elements are lifted, they are also partially rotated. There may be serrations on the undersides of the heads and the faces of the lifting arms may be ratchet-toothed to assist this rotary movement. The jolting and rotary movement cleans the sides of the tubes and knocks off any deposit such as fly ash which may have accumulated on the spiral elements.

The thrust member 10 is at one end located in a carrier plate 12, by two guides 13 slidable through the plate 12. At the other end, it is mounted on a spigot 14 passing through the front of the boiler shell 15 and slidable therein. The thrust member 10 is connected to the spigot 14 by an inverted U coupling 16 to enable the thrust member 10 to be lifted to withdraw it from the carrier plate 12 to permit removal of the cross-head shafts and'elements to give clear access to the flueways.

The thrust member is reciprocated at intervals determined by the total time for which the fan supplying combustion air to the. boiler has been running. A stud 37 projects from the side of'the thrust member and'is engaged by a rotary cam 13 shaped to provide a rapid return motion, of the member 10. This cam is mounted on a shaft 19 rotatedby'a motor 20 which is'controlled by a timing mechanism Zliwhich summates the period of time for which the fan 22 supplying forced air to the boiler runs. The timing mechanism 21 may for example comprise a synchronous electric motor which runs in synchronism with the motor driving the fan 22. After the fan has run for a'prede'termined time, the timingmechanism 21 causes the motor 20 to run for a predetermined period. The cam 18 then causes the thrust member 10 to be reciprocated one or more times.

The motor 2t) may also drive de-clinkering mechanism or may be separate. In the first case, where the declinkering motor may operate at frequent periods of, say, half-an-hour, as may occur in the case of coke combustion, it may be desirable to delay the operation of jolting the spiral elements by the introduction of a variable control on a ratchet-wheel engagement interposed in the driving mechanism between the motor and the cam-shaft so that the elements may be jolted at periods of probably several hours rather than every time the de-clinkering motors actuate.

Means may be provided to operate the jolting mechanism manually. A lever 23 is pivoted to the boiler shell, about the pivot pin 24 and its end engages the end of the spigot 14.

By pulling the lever handle the rocker shafts are actuated to lift and partially rotate the elements and upon releasing the handle sharply the elements fall to jolt them and so remove the deposits.

In the alternative form shown in Figures 3 and 4, a chain 30 passes around sprockets 31 and 32 mounted on a carrier arm 33 mounted above the tubes 1. This arm is pivoted at one end about a shaft 34 which forms the shaft for the sprocket 31 and which is supported in a bracket 35. The other end of the arm 33 rests on a stop 36 and it will be seen that the carrier arm can be raised upwardly from this end to give clear access to the flue passages.

Projecting from the chain 30 is a striker 37 (or if desired a number of such strikers) which engages the levers 9. As the striker 37 passes each row of elements, the appropriate cross shaft 6 is moved to lift and partially rotate the elements 2 and to drop and jolt them as the striker disengages the lever 9 on the cross shaft.

The chain 30 is driven periodically by rotating the shaft 34, in the same manner as the shaft 19 is rotated in the form of Figures 1 and 2. The arrangement of Figures 3 and 4 has an advantage over the Figures 1 and 2 in that only one row of elements is lifted at a time thus reducing the load on the motor as compared with the arrangement of Figures 1 and 2 where all the rows of elements are lifted at the same time.

It will be understood that the invention is not restricted to the details of the preferred forms described by way of example which may be modified without departure from the broad ideas underlying them.

I claim:

1. A boiler comprising a combustion zone, a fan for supplying combustion air to said zone, a series of vertical tubes in communication with said zone and forming flues for the passage of combustion gases from said zone, said tubes being arranged in parallel rows, spiral elements loosely mounted in said tubes to direct the gases in spiral fashion through the tubes, each spiral element having a mushroom head, a pivotally mounted shaft traversing the adjacent tubes in each row, arms projecting from said shaft and positioned under said mushroom heads, levers projecting from said arms and rigid with the shaft means for raising said elements by moving said levers and including thrust means engaging said projecting levers, and means for imparting longitudinal movement to said thrust means and thereby rotate said shafts, whereby the arms lift the spiral elements, said raising means periodically releasing the levers to allow the elements to drop sharply under gravity.

2. A boiler according to claim 1 in which the thrust means comprises a reciprocable member, and a plurality of pins carried by said member, said pins engaging the levers on one stroke of said member and releasing the levers on the return stroke.

3. A boiler according to claim 1 in which the thrust means comprises an endless chain running over sprockets,

and at least one pin projecting from said chain to engage said levers in succession, said pin passing over said levers to allow them to return under gravity.

4. A boiler comprising a combustion zone, a series of vertical tubes in communication with said zone and forming flues for the passage of combustion gases from said zone, said tubes being arranged in parallel rows, spiral elements loosely mounted in said tubes to direct the gases in spiral fashion through the tubes, each spiral element having a mushroom head, a pivotally mounted shaft traversing the adjacent tubes in each row, arms projecting from said shaft and positioned under said mushroom heads, a lever fixed on each of said shafts, means for raising said elements by moving said levers and including thrust means extending transversely of said shafts for engaging the levers of all said shafts, and means for imparting longitudinal movement to said thrust means to swing said levers and thereby rotate said shafts, whereby the arms lift the spiral elements and when said elements have been lifted, said raising means releases the levers to allow the elements to drop sharply under gravity.

5. A boiler according to claim 4 wherein said arms move transversely of said heads when lifting said elements to impart a rotational movement thereto.

6. A boiler comprising a combustion zone, a series of vertical tubes in communication with said zone and forming flues for the passage of combustion gases from said zone, said tubes being arranged in parallel rows, spiral elements loosely mounted in said tubes to direct the gases in spiral fashion through the tubes, eaeh spiral element having a mushroom head, a pivotally mounted shaft traversing the adjacent tubes in each row, arms projecting from said shaft and positioned under said mushroom heads, a lever fixed on each of said shafts, means for raising said elements by moving said levers and including thrust means extending transversely of said shafts for engaging the levers of all said shafts, means for imparting longitudinal movement to said thrust means to swing said levers and thereby rotate said shafts, whereby the arms lift the spiral elements and when said elements have been lifted, said raising means releases the levers to allow the elements to drop sharply under gravity, a fan for supplying combustion air to said combustion zone, a timing mechanism operating in synchronism with the operation of the fan, a driving shaft, a motor for driving said shaft, and a power circuit for said motor and controlled by said timing mechanism to energize said motor to rotate the shaft after a predetermined total time of running the fan, said driving shaft driving said means for imparting movement.

References Cited in the file of this patent UNITED STATES PATENTS 596,381 Reed Dec. 28, 1897 1,460,280 Roth June 26, 1923 1,693,689 Colbiornson Dec. 4, 1928 1,802,023 Kreft Apr. 21, 1931 1,943,622 Piatt Jan. 16, 1934 2,3l1,657 Grindle Feb. 23, 1943 2,653,582 Greger Sept. 29, 1953 

